Air gap thermally stimulated discharge current on unstretched and stretched polypropylene film thermoelectret

Thermally stimulated discharge current (TSDC) in stretched and unstretched polypropylene film was studied. The sample was thermally charged under polarizing fields. After polarization, the samples were discharged by an open-circuit TSDC method. The observed TSDC peaks can be considered due to space charges in the polymer due to its inherent disordered structure. The existence of two well defined peaks reveals tat energetically there exists at least two trapping levels in this polymer. The effect of stretching on the depolarization current is found to decrease at higher stretching percentage. It may be expected that the concentration of the physical deformity which is presumed to be located on the crystalline lamellae is increased on stretching.